The National Transport Authority (NTA) plans to cap the maximum amount charged to bus, train and Luas users in an effort to reward people who switch to public transport.

The details will not be announced until next year, but a spokeswoman said it would benefit commuters who use public transport to make a number of different trips every day.

It is currently being tested on the Luas, but will be expanded to all operators – DART/Commuter trains, Dublin Bus, Bus Eireann and some private coach operators – next year.

"The idea is if you take a number of journeys on, for example, the Luas on the same day, you hit a ceiling and you cannot pay any more," she said.

"It encourages more use of public transport, and also allows people to be more confident of their daily spend, but we're still testing."

Some 182,000 cards have been issued to date after almost one year – 50pc ahead of projections. The cards allow commuters to travel on bus, rail and Luas without having to buy tickets for each leg of a journey.

Instead, they prepay and the cards are waved across magnetic readers at each end of their journey. A computer system calculates the appropriate fare and deducts it from the customer's account.